Luminescent dinuclear gold complexes of bis(diphenylphosphano)acetylene

We have synthesized a series of dinuclear gold(I) derivatives with the diphosphane bis(diphenylphosphano)acetylene, namely [(AuX)2(μ-dppa)] (X=Cl, C6F5, SC6F5, S2CN(CH2Ph)2). X-ray structure determinations for the first three derivatives reveal a linear geometry for the gold centres. There are no intramolecular gold–gold interactions, although for X=Cl intermolecular gold(I)–gold(I) interactions of 3.0694(4) Å lead to an infinite twisted chain; the further presence of C–H⋯Cl contacts leads to a more complex three-dimensional structure. All the derivatives are luminescent in the solid state at low temperature in the range 455–593 nm; most of them are emissive at room temperature in the range 470–598 nm. We have also prepared the dinuclear gold(III) derivative [(Au(C6F5)3)2(μ-dppa)]. Finally, we have prepared the derivative [(AuCl)2(μ-dppa)3], which forms a cage with two tetrahedrically coordinated gold(I) centres at the apical positions bridged by three rigid diphosphane ligands, with a helical twist of 26.2°, and a gold–gold distance of 5.769 Å. The gold(III) and the four-coordinate gold(I) derivatives are not luminescent.